Thanks to Eric Langlay (https://www.youtube.com/user/ericdraven30) for producing, editing, and animating this episode with me. Thanks also to Henry Reich (https://www.youtube.com/user/minutephysics) for his advice and guidance.

Universe Sandbox² : http://universesandbox.com/

Mass vs weight:

https://en.wikipedia.org/wiki/Mass_versus_weightGreat Veritasium video: https://www.youtube.com/watch?v=_Z0X0yE8Ioctwo other great videos: https://www.youtube.com/watch?v=6ccIjRwYO9U and https://www.youtube.com/watch?v=aCqQzrPCcFM

baseballs coming together under gravitational attraction can be simulated in Universe Sandbox 2. More math behind it can be found here: https://www.reddit.com/r/explainlikeimfive/comments/2vyxl7/eli5_will_two_baseballs_a_foot_apart_in_deep/

Why things fall at the same rate: https://www.quora.com/If-an-object-has-more-mass-then-its-pull-on-earth-would-be-greater-than-an-object-with-less-mass-and-therefore-should-fall-to-earth-faster-Why-do-objects-of-different-mass-fall-to-earth-at-the-same-speed